HI - My Jasper ( 27 yo GW female) has had severe arthritis for as long as I have had her (21 years) In fact, she has had two toes on her left foot amputated because the pain could no longer be controlled.
Is your bird on pain relievers? Jasper has been on Metacam for years and now on Celebrex and Gabapentin for five years. Those meds have done a great job of controlling her pain (with no side effects).
She also sleeps in a sleep cage with no perch, but a very thick dog bed. This gives her 12 hours per day of relief of the weight off of her feet and legs.
Acouple Of ideas to help you give your bird a less painful life.